This application is based on Japanese Patent Application Nos. 2001-272802 and 2001-272803, both filed Sep. 7, 2001, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink jet printing apparatus for printing an image on a print medium by ejecting ink from a print head and to an ejection recovery device used in the ink jet printing apparatus to keep ink ejection from nozzles of the print head in good condition.
The present invention can be applied not only to general printing apparatus but also to copying machines, facsimile machines with a communication function, word processors with a printing unit and even industrial printing apparatus combined with a variety of processors.
2. Description of the Related Art
Printing apparatus with functions of a printer, a copying machine and a facsimile, composite type electronic apparatus including computers and word processors, and printing apparatus used as an output device for workstations are designed to print an image on a print medium such as paper and plastic thin films.
Of these printing apparatus, an ink jet printing apparatus, which forms an image by ejecting ink onto a print medium from a print head as a printing means, has the following advantages. That is, the print head can easily be reduced in size, which in turn enables high-speed printing of an image with an enhanced resolution; and the ink jet printing apparatus can print on plain paper without requiring a special treatment of the print medium, thus reducing the running cost. Another advantage is that since the ink jet printing apparatus employs a non-impact system, noise is low. Further, multiple ink colors can be used to form a full color image with ease. In a line type ink jet printing apparatus in which a large number of nozzles are arrayed in a direction of width of the print medium, still faster printing is possible.
Further, in an ink jet printing means (print head) employing a so-called bubble jet (tradename) system that uses a thermal energy to form bubbles in ink and ejects ink by an energy generated by the bubbles, a highly dense nozzle arrangement can be realized which comprises electrothermal transducers, electrodes, liquid paths and a top plate, all formed on a substrate by a semiconductor manufacturing process including etching, vapor deposition and sputtering. The high-density nozzle arrangement allows for a further reduction in size.
The ink jet printing apparatus, however, has a problem that an ingress of air into ink ejection nozzles may dry ink, increasing an ink viscosity and making ink ejection from the nozzles impossible. A known technique to recover the ability of the print head to eject ink is a method that draws out the ink not contributing to the image making from the tips of the nozzles by suction (recovery by suction).
A means for realizing this recovery by suction (suction-based recovery means) consists generally of a cap that can cover the nozzles of the print head air-tightly and a negative pressure generating means that can generate a negative pressure in the cap.
In his specification, the word xe2x80x9cnozzlexe2x80x9d is meant to include a plurality of divided liquid paths for ejecting ink supplied to a common liquid chamber in the print head and ink ejection ports or openings formed at one end of the liquid paths. The word xe2x80x9cinkxe2x80x9d is meant to include visually recognizable color liquids and a print quality enhancement liquid that improves a print quality of that portion of a print medium which is applied with this enhancement liquid.
FIG. 17 shows a recovery device conventionally used in the ink jet printing apparatus. The recovery device shown here includes a cap M5001 arranged in a path on which the print head not shown is moved, a pump M5100 as a negative pressure generating means communicating with this cap, and wiper blades M5011, M5012-1, M5012-2 for removing ink from a nozzle forming surface of the print head.
When a PG motor E0003 rotates in a forward direction, the cap M5001 comes into hermetic contact with the ejection port forming surface of the print head to enclose the nozzles of the print head (capping). Next, when the PG motor E0003 rotates in a backward direction to rotate the pump in a reverse direction, a roller is rotated while in pressure contact with the pump tube, squeezing the pump tube to generate a negative pressure.
This negative pressure acts on the nozzles of the print head through exhaust port M5001a formed in the cap to discharge ink from the cap M5001 and a plurality of suction ports M5005a, M5005b, M5005c formed in a flow path forming member M5005 that covers the exhaust port M5001a. As a result, viscous ink and foam not suited for printing are drawn out of the ejection ports of the print head and further drawn into the suction ports M5005a, M5005b, M5005c provided in the cap M5001 through an ink absorber M5002 for discharging.
Then, the PG motor is driven in the forward direction to cause the cap to part from the ink ejection port forming surface of the print head (decapping), ending a series of suction-based recovery operations.
As shown in FIG. 17 through FIG. 20, the multiple suction ports M5005a, M5005b, M5005c are formed at a plurality of dispersed locations in the flow path forming member M5005 so that the suction ports M5005a, M5005b, M5005c are arranged one between each of different color ink nozzle columns. This arrangement is made to prevent different kinds of ink that have flowed out from different color ink nozzle columns of the print head from crossing other nozzle columns.
The conventional ink ejection recovery device described above, however, still has the following problems that need to be addressed.
A color printing capability and enhanced print quality and resolution required of the ink jet printing apparatus of recent years have increased the number of ink ejection nozzles of the print head and the number of ink colors and also reduced the size of ejected ink droplets considerably. It is therefore necessary to take sufficient care in handling the ink droplets ejected from the print head. For example, if a color ink enters nozzles of different color, these different colors will become mixed (color mixing), failing to produce a normal color printed image. Some countermeasures need to be taken to void this phenomenon.
This color mixing phenomenon easily occurs during the suction-based recovering operation on the print head. Thus, in the conventional technique, suction ports are provided between nozzle columns of different color inks to prevent color inks from getting into the nozzles assigned with different color inks, as described above. This technique has been confirmed to have an effect of alleviating the color mixing but more efforts are needed for minimizing this phenomenon.
To meet this requirement, various methods have been tried. For example, the ink suction is performed separately on nozzle columns of different ink colors by using suction caps dedicated for each color, or a single suction cap is used to draw out ink successively from nozzle columns of different colors, one color at a time. These methods, however, complicate the printing apparatus, resulting in increases in size, cost and suction-based recovery operation time.
In the method that performs the ink suction operations successively with a single cap, the ink staying near the nozzles of the print head is discharged after the suction-based recovery operation is finished until the printing is started, in order to clear the nozzles of unintended or unassigned color inks before starting the printing operation. In this method, too, there is a tendency that as the number of nozzles increases, the amount of ink discharged also increases. This in turn increases a consumption of ink.
The present invention has been accomplished with a view to overcoming the problems of the conventional techniques mentioned above. It is therefore an object of the present invention to provide an inexpensive ejection recovery device capable of simultaneously and efficiently performing suction-based recovery operations using a single cap while preventing different kinds of ink from getting mixed. Another object of the present invention is to provide an ink jet printing apparatus having such an ejection recovery device.
To achieve the above objective, the present invention has the following construction.
According to one aspect, the present invention provides an ejection recovery device in an ink jet printing apparatus comprising: a cap movable toward and away from a print head, the cap being adapted to cover a plurality of ejection ports formed in the print head when it is moved toward the print head; and a pressure generation means connected to an exhaust port formed in the cap to generate a predetermined pressure; wherein when the cap covers the ejection ports, the pressure generation means causes ink to flow out of the ejection ports and be discharged outside the cap through the exhaust port; wherein a plurality of suction ports are formed in the cap and a plurality of paths connecting the plurality of suction ports and the exhaust port have their flow resistances set almost equal.
The paths formed in the cap may be set so that flow speeds of ink passing through the plurality of suction ports are almost equal.
Further, it is also possible to set lengths of the paths almost equal or set cross-sectional areas of the path almost equal.
According to another aspect, the present invention provides an ejection recovery device comprising: a cap movable toward and away from a print head, the cap being adapted to cover a plurality of ejection ports formed in the print head when it is moved toward the print head; and a pressure generation means connected to an exhaust port formed in the cap to generate a predetermined pressure; wherein when the cap covers the ejection ports, the pressure generation means causes ink to flow out of the ejection ports and be discharged outside the cap through the exhaust port; wherein a flow path forming member formed with a plurality of suction ports is fixed to the cap by a predetermined fixing means, the flow path forming member is formed with a plurality of paths connecting the plurality of suction ports and the exhaust port, and the plurality of paths from the suction ports to the exhaust port have almost equal flow resistances.
The flow path forming member may be elastically fixed to an exhaust port forming surface of the cap by the fixing means integrally provided to the cap and having an elasticity. The flow path forming member may form paths in the cap by being combined with the exhaust port forming surface of the cap with which the flow path forming member is brought into intimate contact by an elastic force of the fixing means.
The print head may have ejection portions, one for each kind of ink, each of the ejection portions having at least one column of ejection ports. An arrangement may be made in which when the cap covers the print head, the suction ports of the cap are located near the ejection port columns. For example, if the print head has a plurality of columns of ejection ports for each kind of ink, the suction ports of the cap may each be located between the ejection port columns when the cap covers the plurality of ejection port columns.
According to still another aspect, the present invention provides an ink jet printing apparatus comprising: a printing means having a print head formed with a plurality of ejection ports for ejecting ink; and an ejection recovery device that performs an ejection recovery operation to keep an ink ejection performance of the ejection ports in good condition; wherein the ejection recovery device includes: a cap movable toward and away from the print head, the cap being adapted to cover a plurality of ejection ports formed in the print head when it is moved toward the print head; and a pressure generation means connected to an exhaust port formed in the cap to generate a predetermined pressure; wherein when the cap covers the ejection ports, the pressure generation means causes ink to flow out of the ejection ports and be discharged outside the cap through the exhaust port; wherein a plurality of suction ports are formed in the cap and a plurality of paths connecting the plurality of suction ports and the exhaust port have almost equal flow resistances.
According to a further aspect, the present invention provides an ejection recovery device in an ink jet printing apparatus comprising: a cap movable toward and away from a print head, the cap being adapted to cover a plurality of ejection ports formed in the print head when it is moved toward the print head; and a pressure generation means connected to an exhaust port formed in the cap to generate a predetermined pressure; wherein when the cap covers the ejection ports, the pressure generation means causes ink to flow out of the ejection ports and be discharged outside the cap through the exhaust port; wherein a fixing means is used to fix in the cap a flow path forming member formed with a plurality of suction ports and with a plurality of paths for communicating the plurality of suction ports to the exhaust port.
According to a further aspect, the present invention provides an ink jet printing apparatus comprising: a cap movable toward and away from a print head, the cap being adapted to cover a plurality of ejection ports formed in the print head when it is moved toward the print head; and a pressure generation means connected to an exhaust port formed in the cap to generate a predetermined pressure; wherein when the cap covers the ejection ports, the pressure generation means causes ink to flow out of the ejection ports and be discharged outside the cap through the exhaust port; wherein a fixing means is used to fix in the cap a flow path forming member formed with a plurality of suction ports and with a plurality of paths for communicating the plurality of suction ports to the exhaust port.
According to a further aspect, the present invention provides an ejection recovery device in an ink jet printing apparatus comprising: a cap movable toward and away from a print head, the cap being adapted to cover a plurality of ejection ports formed in the print head when it is moved toward the print head; and a pressure generation means connected to an exhaust port formed in the cap to generate a predetermined pressure; wherein when the cap covers the ejection ports, the pressure generation means causes ink to flow out of the ejection ports and be discharged outside the cap through the exhaust port; wherein a flow path forming member having the suction ports is provided in the cap to form a plurality of paths connecting the suction ports and the exhaust port; wherein the flow path forming member is integrally formed with an engagement means for engaging the ink absorber with the flow path forming member so that the ink absorber capable of absorbing ink can cover the suction ports.
If the print head has ejection portions, one for each kind of ink, each of the ejection portions having at least one column of ejection ports, it is possible to provide a plurality of the suction ports, one for each ejection portion, in the flow path forming member.
The engagement means is preferably arranged to avoid an interference with the ejection ports of the print head. For this purpose, the engagement means may be provided at a position not opposing the ejection ports of the print head.
Further, the engagement means may be a bent retainer portion protruding from a suction port forming surface. The retainer portion is inserted through an insertion hole formed in the ink absorber, and one end portion of the retainer portion holds the ink absorber between it and the flow path forming member. For example, the engagement means may comprise a riser portion rising from one surface of the flow path forming member and a clamp portion integrally formed at one end of the riser portion and facing the one surface of the flow path forming member.
Further, when the suction ports of the flow path forming member and the ink absorber are engaged with each other, it is desired that at least one of the engagement means and the ink absorber elastically deform.
When the suction ports of the flow path forming member and the ink absorber are engaged with each other, it is desired that the positions where the engagement means applies an engagement force to the ink absorber match the suction ports in a planar direction.
The flow path forming member may be elastically fixed to an exhaust port forming surface of the cap by an elastic fixing member integrally provided to the cap.
Further, the flow path forming member forms paths in the cap by being combined with the exhaust port forming surface of the cap with which the flow path forming member is brought into intimate contact by the elasticity of the fixing means.
According to a further aspect, the present invention provides an ink jet printing apparatus comprising: a printing means having a print head formed with a plurality of ejection ports for ejecting ink; and an ejection recovery means that performs an ejection recovery operation to keep an ink ejection performance of the ejection ports in good condition; wherein the ejection recovery means includes: a cap movable toward and away from the print head, the cap being adapted to cover a plurality of ejection ports formed in the print head when it is moved toward the print head; and a pressure generation means connected to an exhaust port formed in the cap to generate a predetermined pressure; wherein when the cap covers the ejection ports, the pressure generation means causes ink to flow out of the ejection ports and be discharged outside the cap through the exhaust port; wherein a flow path forming member having the suction ports is provided in the cap to form a plurality of paths connecting the suction ports and the exhaust port; wherein the flow path forming member is integrally formed with an engagement means for engaging the ink absorber with the flow path forming member so that the ink absorber capable of absorbing ink can cover the suction ports.
The print head generates bubbles in ink by a thermal energy and ejects ink from the ejection ports by an energy of the bubbles.
According to the invention with the above construction, in a print head having a plurality of columns of ejection ports for ejecting different color inks, ejection recovery operations can be performed simultaneously on the multiple columns of ejection ports with a single cap, while at the same time preventing color inks from getting into the ejection ports of different colors. Further, the mixing of colors during the printing operation can be prevented by ejecting small amounts of color inks before starting printing, thus assuring the forming of an image of normal colors. The reduced amounts of color inks to be discharged for the preliminary ejection can minimize an overall consumption of ink.
Further, in this invention since the cap adapted to cover the ejection ports of the print head is formed with paths having the suction ports and since the engagement means is integrally provided on the flow path forming member to engage the ink absorber with the flow path forming member so that the ink absorber covers the suction ports, the ink that was drawn out of the ejection ports of the print head into the ink absorber can be quickly and stably introduced into the suction ports for discharging outside the cap. Hence the sucked-out ink can be prevented from staying in the cap. Therefore, if multiple kinds of ink are ejected from the print head, not only can the mixing of different colors of ink in the print head be minimized but the color inks can also be prevented from getting back into the ejection ports of different colors. As a result, a printed image of normal color can be obtained by performing the preliminary ejection of small amounts of color inks, which in turn leads to a significant reduction in the overall consumption of ink.
Further, since the fixing means integral with the cap holds the flow path forming member in elastic pressure contact with the exhaust port forming surface of the cap, the flow path forming member can be secured reliably and easily without using adhesives.
Furthermore, the paths connecting the exhaust port and the suction ports can be formed inexpensively and easily by bringing the flow path forming member into intimate contact with the exhaust port forming surface of the cap by the fixing means.